In Voice over Packet (VoP) telephony applications, a voice signal is transmitted in the form of data packets at a pre-determined frame rate, such as one packet for every 10 milliseconds. It sometimes is necessary to discard an occasional packet at the receiver of a VoP connection. This may occur, for example, if the local clock at the receiver is slightly slower than the transmitter clock, or if the jitter delay needs to be reduced due to, e.g., a change in network conditions.
Dropping a packet at the receiver has the potential of causing an audible glitch in the output audio signal, since the pitch period of the audio signal is not synchronous with the frame rate. It is therefore desirable to perform packet drops during periods of silence, when no adverse effect on sound quality will occur.